Batteries are widely used in all kinds of electronic products like notebooks, mobile phones, and electric vehicles. Because a single battery usually cannot supply enough power, a plurality of single batteries are connected in series and/or in parallel to increase battery power or output efficiency.
In practice, many electronic products use a battery pack formed by a plurality of batteries connected in series as a power supply. In such case, an internal connection of the whole battery pack should be reliable, in order to avoid impact on power supplying due to a fault of a single battery. Otherwise, charging and discharging of the battery pack may be seriously affected and security of the battery pack cannot be guaranteed. Especially for a battery pack formed by lithium batteries, it usually needs a battery management system to detect the internal connection of the whole battery pack before starting the battery pack. Conventionally, a voltage of each battery of the battery pack is measured by a detecting device, and then the voltage is compared with a preset value to judge whether the battery has a fault. However, measuring the voltage by the detecting device needs an electric wire (i.e., a detecting line) to connect the battery and the detecting device. Because a distance between the battery and the detecting device is usually comparatively long, a comparatively long electric wire is easier to break down. However, an electric wire inside of the detecting device is comparatively short and thus it is not easy to break down. When the detecting device is connected to the battery via the electric wire, if a fault (such as an open circuit) is detected between both ends of a single battery, it's hard to judge whether the fault is caused by the single battery or by the electric wire.